Vorticity cancellation at trailing edge for induced drag elimination

Abstract

Wing tip vortices are evident from airliner vapor trails, and helicopter blade slap. Elliptically loaded high aspect ratio tapered wings have minimum induced drag but cannot eliminate it. Different methods are disclosed herein, for upper and lower surface boundary layers to cancel their opposing vorticity upon shedding from the trailing edge, thereby eliminating wake vorticty, induced drag and associated noise. This requires wing-rotor-propeller or fan blades with a platform designed for uniform bound circulation and with boundary layer control near the tip. In addition this requires special techniques to counter span-wise pressure gradients, such as tip circulation control blowing or an upwind small propeller or wind turbine on each tip. These techniques can eliminate wake vorticity with its induced drag, noise, flying on the backside of the power curve and the option for asymmetric loading by pneumatic means to eliminate need for cyclic pitch control or conventional ailerons.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of Invention[0002]This invention relates to methods for a lifting body to eliminate induced drag and noise, by canceling the vorticity, generated in its upper and lower surface boundary layers, upon leaving the trailing edge, thus keeping it out of the wake. This technology applies to any lifting body such as a wing, helicopter rotor, propeller, fan blade, etc.[0003]2. Prior Art[0004]A powerful relation in theoretical aerodynamics was developed independently by German mathematician W. Kutta (1867–1944) and Russian mathematician N. Jouwkowski (1847–1921) and is called the Kutta-Joukowski theorem for a two-dimensional (2-D) lift producing body in an ideal fluid, which has no viscosity. Such a body produces lift per unit span equal to the sum of the up wash momentum in front of and the equal but opposite downwash momentum behind the lifting body. The lift per unit span produced is given in vector form by {right arrow over (L)}=ρ({right arrow ov...

AI Technical Summary

Benefits of technology

[0037]In accordance with the present invention, the methods required to cancel the upper and lower surface boundary layer vorticity upon shedding from the trailing edge of a finite wing or rotor blade has been described in detail. To accomplish this feat with an elliptically loaded wing would require far more suction power than the potential gain in thrust power savings. Only by configuring the finite wing or rotor blade to have constant bound circulation, so that the upper and lower surface boundary layer vorticity cancels each other upon shedding from the trailing edge, will the power required reduce to less than 10% of the thrust power saved. This makes it a desirable technology for future aircraft, helicopters, propellers and fans.

Problems solved by technology

These methods do not contradict Hemholt's theorems which state that vorticity cannot be terminated within an ideal fluid.

Then deflecting both ailerons upwards will reduce their effective angle of attack.

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